A video cassette recorder (VCR) is a device that records television programs on magnetic tape cassettes, and plays back recorded programs on a television set. VCRs can generally be programmed by a user to record the program or programs being broadcast on a particular channel for a specified period of time on a particular date.
1. Field of the Invention
The present invention relates to recording television signals, more particularly to a mechanism for programming the record times for a video cassette recorder.
2. Description of the Prior Art
One method of programming a VCR to record television programs includes a user manually keying in the channel, the start time, the stop time for recording, and the date (the date is not always necessary if the recording is made on the same day). This manual programming of the VCR is usually performed by using keys located on the VCR itself or by using keys on a remote control console.
An alternative method of manually programming the channel and the start and stop times of a VCR recording is to use an electronic program guide (EPG) that is displayed on a television set. An EPG displays information about television programs scheduled to be broadcast. The date, times, and channel for each program are generally displayed by an EPG. Many EPGs allow users to select a particular program listing (by clicking on the listing, for example) to be recorded by a VCR connected to the television system. After a program listing has been selected on such an EPG, the VCR is automatically programmed in accordance with the channel, date, and start and end times, which are stored in the EPG in association with the selected program listing.
This method of using an EPG to program a VCR is usually more convenient than the manual method, because the user does not have to look up the start and stop times and the channel for a program that he/she wishes to record. However, EPGs are not always available to users who do not subscribe to a special television broadcast system (e.g. cable or satellite systems) and want to record programs being transmitted through conventional television antenna signals.
When programming a VCR in accordance with either one of the above methods, a problem may arise if the television program to be recorded starts and/or ends at a different time than was originally scheduled. Such deviations from the scheduled times may cause part of the television program to be broadcast outside the programmed recording time interval, resulting in an incomplete recording.
FIG. 1 is illustrative of such a problem. FIG. 1 shows an example of the scheduled broadcast times for programs on this channel between 3:00 pm and 6:00 pm, and the actual program times due to a particular program (Program A) not ending on time. Suppose a user wants to record Program B on a VCR. The user will program a VCR to record from the scheduled start time 1 of 4:00 pm to the scheduled stop time of 5:00 pm (as indicated by the hatched time interval). As shown by the actual broadcast time line, however, the actual start time 1a and stop time 2a for Program B come after the scheduled start and stop times 1 and 2. Therefore, the VCR will record a portion 3 of Program A, and will omit a portion 4 of Program B.
As shown in FIG. 1, if the preceding television program runs too long, a VCR recording may not record the entire television program that was programmed to be recorded. This sometimes occurs when a previous program is a televised sports events such as football or baseball matches which tend to last longer than their scheduled time (e.g., the match goes into extra time or extra innings). Generally, television networks will televise an entire sports event, even if they go beyond their allotted programming time. However, such delayed start times may also occur due to the broadcasting of important late-breaking news, or other unscheduled programs.
The problem of incomplete television program recordings may also occur if the time kept by the internal clock of the VCR deviates from the actual time, or from the time kept by the broadcasting station or network. For instance, a user may set the VCR's clock such that it runs several minutes fast or slow. Alternatively, the broadcasting network or station may not be keeping accurate time. The lack of synchronization between the VCR's clock and the network or station's clock may cause part of the program to be broadcast outside the recording times of the VCR.
Program Delivery Control (PDC) offers a solution to the above problem. PDC systems control compliant VCRs, and other types of video recorders, in accordance with to teletext codes transmitted by the broadcaster corresponding to each television program. A video recorder under PDC control does not start recording until it receives a PDC code, which is transmitted just before the television program begins. Therefore, if the program is delayed or re-scheduled, the recording of the VCR will automatically be re-scheduled so that nothing of the television program is missed. However, PDC requires a teletext service and is not available to all television viewers, especially to those whose television sets receive programs through conventional antenna signals.